Air/vapour separation device

ABSTRACT

A device for separating gas entrained in a flow of liquid. The device comprises a main housing having a liquid inlet and a liquid outlet. A separation chamber is disposed within the housing between the inlet and the outlet, the gas entrained in the flow of liquid being separated from the flow of liquid when the flow of liquid passes from the inlet to the outlet within the separation chamber. A vent passage extends from the separation chamber. A main valve within the housing controls the flow of liquid between the inlet and the outlet. A detector including a dual orifice arrangement disposed in the vent passage detects the presence of a gas in the vent passage. A pilot valve is coupled to the detector and to the main valve for controlling the main valve as a function of the presence of gas in the vent passage. A first control passage is disposed within the housing for coupling the pilot valve to the dual orifice arrangement.

FIELD OF THE INVENTION

This invention relates to a device for the separation of gas which maybe entrained in a flow of liquid. Preferably, the device also controlsthe amount of gas that is expelled in the liquid that is dispensed fromthe device.

BACKGROUND OF THE INVENTION

In many applications it is important to measure accurately the volume ofliquid passing through a pipe or tube, for example a fuel dispenser,such as a petrol pump. If the liquid is contaminated with gas, such asair, vapour and/or other gas, the meter, which cannot differentiatebetween the liquid and the gas, will produce an erroneous reading forthe volume of liquid dispensed. Thus the purchaser of the fuel will paynot only for the fuel actually dispensed, but also for any gas entrainedin the fuel flow line.

It is known, for example from Australian Patent No. 460441, to provide adevice in the fuel flow line to separate the gas from the liquid byarranging for the liquid to flow through a separation tank, locatedupstream of the meter, in which any gas can rise to the top and fromwhich liquid is drawn from the bottom. Exit of liquid out of the tank isvia a main valve which is controlled either by a pilot valve or by anorifice to close the main valve when there is a substantial volume ofgas in the tank. This gas escapes from the tank via a vent passage to anair separation sump, the tank replacing the escaping gas with furtherliquid or liquid/gas mixture. When the pilot valve or orifice sense thatthe liquid/gas mixture in the tank has again reached a certain level,the main valve is opened to allow liquid to flow at normal operatinglevels.

Although the above-described device works reasonably well, it needs tobe built into the liquid dispensing system with the various valves andthe orifice being interconnected by pipes or hoses which requires asubstantial investment and a relatively large amount of space.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a devicefor separating gas from liquid, which is more compact, has a smallnumber of components, is cheap to manufacture and which willautomatically adapt to the requirements of liquids of differentviscosities, densities and/or flowrates.

Accordingly, the invention provides a device for separating gasentrained in a flow of liquid, the device comprising a main housinghaving a liquid inlet and a liquid outlet, a separation volume withinthe housing between the inlet and the outlet, a vent passage extendingfrom the separation volume to the outside of the housing, a main valvewithin the housing for controlling flow of liquid between the inlet andthe outlet, means for detecting the presence of gas in the vent passage,a pilot valve coupled to the detecting means and the main valve forcontrolling the main valve in dependence on the presence of gas in thevent passage.

In a preferred embodiment, the detecting means is a dual orificearrangement in the vent passage and the pilot valve is coupled to thedual orifice arrangement via a first control passage within the housing.The dual orifice arrangement is preferably removable from the ventpassage.

In a preferred embodiment of the invention, the pilot valve is a poppetvalve operated by a diaphragm which is caused to close when gas isdetected in the vent passage. The pilot valve is preferably arranged toclose a second control passage extending between the main valve, whichis preferably a diaphragm valve, and an inlet downstream of the mainvalve. The second control passage is preferably coupled to the mainvalve on the downstream side such that, when the second control passageis open, pressure on the downstream side of the diaphragm is smallerthan on the upstream side, thereby causing the diaphragm to be openedagainst the action of a biasing means, such as a spring. When, however,the second control passage is closed by the pilot valve, the pressure onthe downstream and upstream sides of the diaphragm is equalised by meansof a bleed connection between the two sides of the diaphragm. The bleedconnection is preferably a bleed orifice in the diaphragm, but could,alternatively, be a bleed passage within the housing.

BRIEF DESCRIPTION OF THE DRAWING

The invention will now be more fully described, by way of example, withreference to the drawings, of which:

FIG. 1 is a schematic diagram of a gas detection system incorporating agas separation device according to one embodiment of the presentinvention;

FIG. 2 is a top view of one embodiment of gas separation apparatusaccording to the invention;

FIG. 3 is a view of one end of the apparatus of FIG. 2;

FIG. 4 is a view of the other end of the apparatus of FIG. 2;

FIG. 5 is a cross-sectional view on line V--V in FIG. 3;

FIG. 6 is a cross-sectional view on line VI--VI in FIG. 3; and

FIG. 7 is an enlarged part cross-sectional view of a portion of a secondembodiment of an apparatus according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1, the system comprises a pump 2 having coupled theretoan integrated gas separation device 3, which consists of a gas separator4, a gas detector 5 formed by a dual orifice, a pilot valve 6 operatedby the gas detector 5 and a main flow valve 7 controlled by the pilotvalve 6. Also coupled to the pump 2 is an air separator sump unit 8,used to expel any gas present and return liquid to the pump inlet.

The pump 2, which is a suction pump, draws fuel, which may have gasentrained therein, from a tank 1 through pipe 9a and supplies the fuelto the gas separation device 3 through passage 9b.

The fuel first enters a passive separator 4 where the fuel velocity isreduced through a baffle 10. This allows time for any entrapped gases torise and escape with fuel through passage 11 to the dual orifice gasdetector 5. The main flow of substantially gas free liquid exits throughpassage 12 to the main flow valve 7.

The gas detector 5 has an inlet orifice 13 and an outlet orifice 15separated by a chamber 14. When substantially gas free fuel from theseparator 4 passes through the inlet orifice 13 and across chamber 14 ina stream to enter the outlet orifice 15, a low pressure (partial vacuum)is created in chamber 14. The fuel flows through passage 16 from theoutlet orifice 15 to the air separator sump unit 8.

In the air separator sump unit 8 any gases are expelled and the liquidfuel is returned to the pump inlet by tube 19. The flow of returningfuel is controlled by valve 17 which is operated by float 18.

Chamber 14 is connected by passage 20 to a chamber 21 containing adiaphragm 22 of the pilot valve 6. The low pressure acts on thediaphragm 22 in the chamber 21 and opens a popper valve 23 against theaction of pump pressure and spring 24. The opening of poppet valve 23allows fuel to flow from passage 28 to passage 29.

Fuel flow through passage 28 and 29 is controlled by an orifice 26formed in diaphragm 25 in main flow valve 7. This flow creates apressure drop across diaphragm 25 in main flow valve 7. When thepressure drop across the diaphragm 25 is great enough to overcome thebias of a spring 27 the main flow valve 7 opens. Fuel can now flow fromthe separator 4 via passage 12 to passage 32 to a fuel meter, and thento a hose and nozzle where it is dispensed.

Any gas in the fuel is concentrated in the fuel gas mixture exiting theseparator 4 through passage 11 to the dual orifice gas detector 5. Thepresence of gas in the liquid entering the detector 5 causes a suddenincrease in pressure in chamber 14 between the orifices 13 and 15, thepressure changes from a partial vacuum to a positive pressure. This iscaused by the expansion of the gas after orifice 13, due to the pressuredifference across the inlet orifice 13 breaking up the liquid stream sothat it does not cleanly enter the second orifice 15.

The pressure increase is transmitted along passage 20 to chamber 21,this reduces the pressure on the pilot valve diaphragm 22. This allowsthe spring 24 to close the pilot valve, stopping the flow of fuel alongpassages 28, and 29 and through orifice 26. The stopping of flow throughthe orifice 26 in diaphragm 25 allows the pressures to equalise on eachside of diaphragm 25. The spring 27 now pushes the flow valve 7 closed.No fuel is dispensed while there is gas being expelled from theseparator 4 via passage 11. This ensures that the amount of gas meteredand dispensed is not in excess of the required limits.

As shown in FIGS. 2 to 6 of the drawings, a first embodiment of anapparatus comprises a main housing 101 comprising a generally hollowcylinder 102 arranged to be mounted in a fuel dispensing pump upstreamof the fuel meter. The fuel, which may have gas, such as air or vapourentrained therein enters the housing through inlet 103 into a separationvolume 104 where the flow is reduced so that any gas can rise to the topof volume 104 and escape through vent passage 105. The main flow ofliquid passes through a main valve 106 to outlet 107, which is connectedto the meter (not shown) and a fuel nozzle (not shown).

The liquid flows from separation volume 104 via a main valve inlet 108into a main outlet passage 109. The main valve 106 comprises a diaphragm110 biased by spring 111 to close the main outlet passage 109. A bleedaperture 119 is provided between the upstream and downstream sides indiaphragm 110 so as to equalise the pressure. When this happens, theforce of spring 111 biases the diaphragm 110 to the closed position, asshown in FIG. 6.

Within vent passage 105, there is provided a gas detector 112. The gasdetector 112 comprises an inlet orifice and an outlet orifice separatedby a chamber. As long as only liquid flows through vent passage 105, andtherefore through gas detector 112, a low pressure (partial vacuum) iscreated in the chamber due to the liquid stream passing straight intothe outlet orifice. The low pressure is coupled to a pilot valve 113 viafirst control passage 114. The pilot valve 113, which includes adiaphragm 115 connected to a ball valve 116, is arranged to open andclose a second control passage 117 extending from the main valve 106 onthe downstream side of diaphragm 110 to the main outlet passage 109. Thesecond control passage 117 therefore comprises a first portion 117aextending from the main valve 106 to an inlet of pilot valve 113, and asecond portion 117b extending from an outlet of pilot valve 113 to mainoutlet passage 109. The ball valve 116, controlled by diaphragm 115, andbiasing means, such as a spring 118, opens and closes the pilot valve113. The first control passage 114 is arranged to open pilot valve 113,by coupling reduced pressure on one side of the diaphragm 115, when thepartial vacuum extends through first control passage 114 due to liquidpassing through vent passage 105 and detector 112.

When pilot valve 113 is open, liquid is allowed to flow through secondcontrol passage 117 and therefore reduces the pressure on the downstreamside of diaphragm 110 of main valve 106. Therefore, pressure on theupstream side of main valve 106 forces diaphragm 110 to open against thebias spring 111.

When, however, gas separates from the liquid fuel in separation volume104, the gas rises to the top of the volume and escapes through ventpassage 105. The presence of gas causes a sudden increase in pressure inthe chamber between the two orifices due to the pressure differenceacross the inlet orifice causing expansion of the gas. The expanding gasbreaks up the liquid steam so that it does not enter the outlet orificecleanly. Therefore the pressure on either side of diaphragm 115 of pilotvalve 113 is equalised, thus closing pilot valve 113. When pilot valve113 is closed, as described earlier, pressure on either side ofdiaphragm 110 of main valve 106 is equalised through bleed aperture 119so that diaphragm 110 is biased closed by spring 111, thus closing themain valve 106.

The main valve 106 thus remains closed until all the gas separated fromthe liquid in separation volume 104 has escaped through vent passages105 and liquid once again flows through detector 112 causing reducedpressure in first control passage 114 so as to open pilot valve 113 andthus main valve 106.

It will be apparent that in certain circumstances it will not berequired to turn off the main valve when gas completely separates fromliquid in volume 104 and therefore detector 112 is made easilyremovable, whereupon first control passage 114 can be capped off.

FIG. 7 shows part of a second embodiment of a gas separation deviceaccording to the invention. There is shown a portion of a separationvolume 204 and a vent passage 205 leading to a gas detector 212 havingan inlet orifice 220 and an outlet orifice 221 separated by a chamber222. The chamber 222 is coupled via a control passage 214 to a chamber223 in which is arranged a diaphragm 215 of a pilot valve 213. Thediaphragm 215 is coupled to a poppet valve 224 biased to a closedposition by spring 218. When a reduced pressure is coupled from chamber222 via passage 214 to chamber 223, the pressure difference between thetwo sides of diaphragm 213 causes the poppet valve 224 to be openedagainst the bias of spring 218.

Poppet valve 224 closes a control passage 217 coupled to a downstreamside of a diaphragm 210 of a main valve 206. When the poppet valve 224is closed, pressure on either side of diaphragm 210 is equalised via anaperture 219 in the diaphragm 210, causing the main valve to be biasedclosed by a spring 211. However, when the poppet valve 224 is open, theflow of liquid through control passage 217 reduces the pressure on thedownstream side of diaphragm 210, causing the pressure on the upstreamside to open the diaphragm against the bias of spring 211 and thereforeopen the main valve 206 to flow of fuel through main valve inlet 208 tomain fuel outlet 207. It will be appreciated that other features of thesecond embodiment of the gas separation apparatus are similar to thosedescribed earlier.

It will be clear, therefore that the present invention provides a muchmore compact modular construction of a device for separating gas fromliquids than was previously the case.

We claim:
 1. A device for separating gas entrained in a flow of liquid,the device comprising a main housing having a liquid inlet and a liquidoutlet; a separation chamber disposed within the housing between theinlet and the outlet, the gas entrained in the flow of liquid beingseparated from the flow of liquid when the flow of liquid passes fromthe inlet to the outlet within the separation chamber; a vent passageextending from the separation chamber; a main valve within the housingfor controlling the flow of liquid between the inlet and the outlet;means for detecting a presence of a gas in the vent passage comprising adual orifice arrangement disposed in the vent passage; a pilot valvecoupled to the means for detecting and to the main valve for controllingthe main valve as a function of the presence of gas in the vent passage;and a first control passage within the housing for coupling the pilotvalve to the dual orifice arrangement.
 2. A device according to claim 1,wherein the dual orifice arrangement comprises an inlet orifice and anoutlet orifice separated by a dual orifice chamber coupled to the firstcontrol passage.
 3. A device according to claim 2, wherein the pilotvalve comprises a pilot valve chamber including a diaphragm operatedpoppet valve having a diaphragm and a biasing means for biasing thediaphragm, the first control passage being coupled to the pilot valvechamber such that, when gas does not flow through the dual orificearrangement, a reduced pressure is produced in the pilot valve chamber,the reduced pressure being coupled to one side of the diaphragm so thatthe difference in pressure between both sides of the diaphragm causesthe diaphragm to move and open the pilot valve against a bias of thebiasing means, and when gas does flow through the dual orificearrangement, pressure in the chamber is not reduced and the pilot valveis closed by the bias of the biasing means.
 4. A device according toclaim 1, wherein the dual orifice arrangement is removable from the ventpassage.
 5. A device according to claim 1, wherein the pilot valve is adiaphragm operated valve which is caused to close when gas is detectedin the vent passage.
 6. A device according to claim 1, wherein the mainvalve is a diaphragm operated valve.
 7. A device according to claim 1,and further including a second control passage extending between themain valve and an outlet upstream of the main valve wherein the pilotvalve is effective for closing the second control passage.
 8. A deviceaccording to claim 7, wherein the main valve comprises a diaphragmoperated valve including a diaphragm, a biasing means for biasing thediaphragm, and a bleed connection between the two sides of thediaphragm, the diaphragm having an upstream side and a downstream side,and wherein the second control passage is coupled to the main valve onthe downstream side of the diaphragm such that, when the second controlpassage is open, pressure on the downstream side of the diaphragm issmaller than pressure on the upstream side of the diaphragm, therebycausing the diaphragm to be opened against a bias of the biasing means,and when the second control passage is closed by the pilot valve,pressures on the downstream side and on the upstream side of thediaphragm are equalised by the bleed connection.
 9. A device accordingto claim 8, wherein the bleed connection is a bleed orifice in thediaphragm.
 10. A device according to claim 8, wherein the bleedconnection is a bleed passage within the housing.